The sort the speaker is used to.
People from the BSDophilic academic community are likely to issue
comments like "System V? Why don't you use a real
operating system?", people from the commercial/industrial Unix
sector are known to complain "BSD? Why don't you use a
real operating system?", and people from IBM object
"Unix? Why don't you use a real operating system?" Only
MS-DOS is universally considered unreal. See holy wars,
religious issues, proprietary,